Us, of course.  And now according to the Sightline Institute:

Sightline 2

Altogether, Sightline tabulates 4,920 car-sharing vehicles in Cascadia. That’s just 0.4 percent of these cities’ estimated 1.4 million motor vehicles, but at any moment on city streets, more than 1 percent of moving vehicles are typically car-shares, because shared vehicles are driven much more of the time than private cars, which on average sit parked more than 23 hours a day. In the cities’ dense, close-in neighborhoods, car-shares account for an even larger share of moving autos, sometimes as much as 5 percent—an impressive change in just a decade or two.

Portland Seattle Vancouver, BC
   Modo 450
   Zipcar 225 312 225
   Car2Go 500 750 1,275
   Evo 600
   ReachNow 370
   Getaround 90
   Turo 43 80
Total 858 1,512 2,550